#define _CRT_SECURE_NO_WARNINGS	

#include<stdio.h>



int main()
{
    int n;
    scanf("%d", &n);
    double sum = 0;
    for (int i = 1; i <= n; i++)
        sum += (2 * i - 1) * 1.0 / (2 * i);
    printf("%.2lf", sum);
    return 0;
}